#include <stdio.h>

int main()
{
	int x = 0;
	int y = 0;
    scanf ("%d %d",&x,&y);
    if((x<=1&&x>=-1)&&(y<=1&&y>=-1)) 
    {
    	printf("yes");
	}
        
    else
    {
    	printf("no");
	}
	
	return 0;
}
